1. Field of the Invention
The present invention relates to a mobile robot having a plurality of movable links extended from a base body.
2. Description of the Related Art
As a mobile robot having a plurality of movable links extended from a base body thereof, there has conventionally been known in general a humanoid robot provided with two leg links and two arm links as movable links, as described in, for example, Japanese Patent No. 3555107 (hereinafter referred to as “Patent Document 1”).
This type of a mobile robot is configured such that the distal end parts of the movable links are moved with respect to the base body by the motions of the joints provided between the distal end portions of the movable links and the base body.
Further, when traveling on a level ground or the like, the mobile robot usually travels in the direction of the front side of the base body thereof while observing the conditions in an external world on the front side of the base body of the mobile robot, i.e. external world ahead in a traveling direction of the mobile robot, by a camera or the like.
In recent years, a mobile robot, such as the one described in Patent Document 1, has been expected to be capable of traveling in a variety of environments rather than being limited to a smooth environment, such as a level ground.
However, conventional mobile robots are designed on the basis of an assumption that they will travel mainly in smooth environments, such as level grounds. Hence, if the mobile robots are operated in a variety of environments, then interference between the parts of the mobile robots and objects in the external world tends to take place.
More specifically, the leg links of the mobile robot as described in Patent Document 1 are normally configured such that the middle portions (e.g. the knees) are bendable so as to jut out to the front side of the base body. Therefore, when the mobile robot is instructed to climb up a relatively high step or to climb up or down a ladder or a stepladder, the leg links easily interfere with the step, the ladder or the stepladder.
Further, when the mobile robot is instructed to travel on, for example, an irregular terrain or the like in a state in which the mobile robot supports its own weight by the leg links and the arm links thereof (hereinafter referred to as “the multi-legged state” in some cases), the middle portions of the leg links tend to interfere with projections on a floor or the base body thereof.
Thus, a situation in which it is difficult for the mobile robot to travel frequently occurs.
As a conceivable solution to such an inconvenience, the leg links, for example, could be configured such that the middle portions thereof are bendable toward the rear side, as well as the front side, of the base body.
Inconveniently, however, such a solution will easily result in a complicated construction of each leg link or an increase in size or weight of each leg link to enhance the rigidity of the leg link. There will be another inconvenience in which the singularity state of the leg links easily occurs.
Further, when the mobile robot is instructed to, for example, climb up a relatively high step, the mobile robot could be instructed to travel in the direction of the rear side of the base body (i.e. the mobile robot could be instructed to travel backward). Alternatively, when the mobile robot is instructed to climb up or down a ladder or the like, the mobile robot could be instructed to climb up or down the ladder or the like with the rear side of the base body thereof facing the ladder or the like. Further alternatively, when the mobile robot is instructed to travel in the multi-legged state, the mobile robot could be instructed to travel with the rear side of the base body thereof facing a floor surface.
In such cases, however, it will be required to add a device that permits the observation of the conditions of the external world on the rear side as well as the front side of the base body of the mobile robot.
In addition, the arm links of the mobile robot are normally configured such that the distal end portions thereof can be moved over an extensive range on the front side of the base body. In many cases, the movable range of the distal end portions of the arm links on the rear side of the base body inevitably becomes limited.
Hence, when the mobile robot is to climb a relatively high step, if the mobile robot is instructed to travel in the direction of the rear of the base body thereof, then it will be necessary to switch the direction of the mobile robot at a destination after the travel. This will require a space for accomplishing the switching of the direction. Further, if the mobile robot is instructed to climb up or down a ladder or the like with the rear side of the base body thereof facing the ladder or the like, or when the mobile robot is instructed to travel in the multi-legged state, it will be usually difficult to properly move the arm links.